1. Field of the Invention
The present invention relates to an MPEG data recording apparatus such as a digital VTR, and more particularly to record control of MPEG data (which will hereinafter imply MPEG-TS data or MPEG-PTS data) input from the outside through an IEEE 1394 interface circuit (which will be hereinafter referred to as an IEEE 1394 interface).
2. Description of the Background Art
A conventional MPEG data recording apparatus will be described with reference to FIG. 8 by taking a D-VHS apparatus as an example.
FIG. 8 is a block diagram (prior art) selectively showing a portion to be operated in a system of a D-VHS apparatus when MEPG data input through an IEEE 1394 network are to be recorded.
In FIG. 8, the reference numeral 1 denotes an IEEE 1394 interface (a serial interface circuit having the function of real time transmission) connected to a DTV (Digital TV) 12 through an IEEE 1394 network 100. The IEEE 1394 interface 1 exchanges asynchronous data such as an AV/C command and isochronous data such as an MPEG-partial transport stream (PTS) or an MPEG-transport stream (TS) together with the DTV 12. The reference numeral 2 denotes a D-VHS data processing section or a data recording section for fetching the MPEG data output from the IEEE 1394 interface 1, converting the fetched MPEG data into data having a D-VHS data format and recording the same data. The reference numeral 3 denotes an ECC processing section for adding an error correction code (ECC) to the D-VHS data converted through the D-VHS data processing section 2. The reference numeral 4 denotes a buffer memory for temporarily storing the D-VHS data during an ECC processing. The reference numeral 5 denotes a recording signal processing section for D/A converting the D-VHS data having the ECC added thereto in the ECC processing section 3 into a recording signal which can be recorded on a magnetic tape. The reference numeral 6 denotes a recording amplifier for amplifying the recording signal and the reference numeral 7 denotes a recording head for recording the amplified recording signal on the magnetic tape. The reference numeral 8 denotes a magnetic tape on which the recording signal is to be recorded and the reference numeral 9 denotes a motor driver for regulating a running speed of the magnetic tape 8. The reference numeral 10 denotes a data rate detecting section for detecting a data volume (data rate) input per unit time based on the MPEG data output from the IEEE 1394 interface 1. The reference numeral 11 denotes a recording mode control section for adaptively switching a recording mode to control both sections 5 and 9 based on the data rate of the input MPEG data which is detected by the data rate detecting section 10. A portion including these components 1 to 11 constitutes a part of the MPEG data recording apparatus.
The reference numeral 12 denotes an external digital television (DTV) to be connected to the MPEG data recording apparatus through the IEEE 1394 network 100.
The operation of the conventional MPEG data recording apparatus will be described below. First of all, distributed MPEG data to be input from the DTV 12 into the D-VHS apparatus through the IEEE 1394 network 100 are received by the IEEE 1394 interface 1, and the IEEE 1394 interface 1 recomposes the MPEG data thus received and sends the recomposed MPEG data to the D-VHS data processing section 2 and the data rate detecting section 10.
Next, the D-VHS data processing section (data recording section) 2 converts the received MPEG data into data having a data format in conformity with a D-VHS standard, and realigns and records the data, and outputs the recorded D-VHS data to the ECC processing section 3.
Next, the ECC processing section 3 once stores the MPEG data (D-VHS data) converted to have the data format of the D-VHS standard in the buffer memory 4, and then adds an error correction code to the D-VHS data read from the buffer memory 4 and outputs the D-VHS data having the error correction code added thereto to the recording signal processing section 5.
Then, the recording signal processing section 5 carries out a partial response signal processing (PRML: Partial Response Maximum Likelihood) for recording the received D-VHS data on a magnetic tape for the D-VHS data, and outputs the D-VHS data subjected to the PRML processing as a recording signal to the recording amplifier 6.
The recording amplifier 6 amplifies the received recording signal and outputs the amplified recording signal to the magnetic head 7. The magnetic head 7 records the amplified recording signal thus received onto the magnetic tape 8.
On the other hand, the data rate detecting section 10 detects the data rate of input data based on the received MPEG data and transmits the result of the detection to the recording mode control section 11. Consequently, the recording mode control section 11 selects a proper recording mode which is sufficient for recording the input data and can minimize an amount of tape consumption based on the result of the recording mode detection, and carries out control for recording in the recording mode thus selected, that is, control of a tape running speed through the motor driver 9 and control of a recording signal format through the recording signal processing section 5, header data and the like.
FIG. 9 is a conceptual diagram (prior art) showing an example of a communication to be carried out between the DTV 12 and the MPEG data recording apparatus in the case in which a user performs a recording operation by using a control panel display on a screen of the DTV 12.
As shown in FIG. 9, in the case in which the user is to operate the DTV 12 to record, in the MPEG data recording apparatus, a digital broadcast (MPEG data) which is being received, he (she) first establishes a connection between the DTV 12 and the MPEG data recording apparatus through the IEEE 1394 network 100 by using the control panel display provided in the DTV 12. In general, when the IEEE 1394 connection is established between both apparatuses, an input/output path related to isochronous data (a channel for isochronous data on the IEEE 1394) is formed therebetween and the DTV 12 immediately starts to deliver, to its own output path, the MPEG data which are being received. As a result, the IEEE 1394 interface 1 receives the MPEG data which are being delivered.
In this stage, however, the MPEG data recording apparatus does not start the recording operation. The user carries out the recording operation (press-down of a recording button or the like) through the control panel display or the like after the establishment of the IEEE 1394 connection, and the MPEG data recording apparatus then starts the recording operation.
The recording operation of the user is basically carried out through transmission of a recording control code using a path for asynchronous data on the IEEE 1394 network 100. Before or after the transmission of the recording control code itself, a communication for confirming mutual states and situations is carried out between the MPEG data recording apparatus and the DTV 12. The reason is that whether a recording medium is inserted in the MPEG data recording apparatus or whether the MPEG data recording apparatus can be switched into a recording operation is to be confirmed before switching into the recording operation, for example. In order to carry out a series of confirming operations, some time lag is generated before the recording operation is actually started after the user carries out the recording operation (the press-down of the recording button or the like).
As described above, in the conventional MPEG data recording apparatus, it is necessary to take a processing time for a communication through the exchange of control data or the like after the user manipulates to carry out recording with intention. Therefore, there is a problem in that the recording operation can be started with some time delay.